One example of a superheated steam generator of an electromagnetic induction type is disclosed in Japanese Publication for Unexamined Patent Application No. 303702/1997 (Tokukaihei 9-303702; published on Nov. 28, 1997), in which generated steam is superheated to obtain superheated steam of about 500° C.
In this superheated steam generator, a ceramic insulator is provided around a copper tank through which generated steam passes, and a coil connected to a high-frequency AC power supply is disposed around the ceramic insulator, the coil being part of coolant circulating piping.
Energizing the coil creates magnetic field lines through the tank, which generates eddy currents through the tank and produces Joule heat therein. The steam is superheated as it passes through the tank, thus producing superheated steam that far exceeds 100° C. in temperature.
The superheated steam so produced by the superheated steam generator requires different temperature settings for different uses, which may be food processing such as thawing, baking, boiling, and deoiling, or other areas of applications such as disinfections and drying.
One drawback of the superheated steam generator of the foregoing publication is that the Joule heat produced by the magnetic field lines brings an abrupt increase of temperature in the tank. It is therefore extremely difficult to control the temperature only by turning on or off the power supply. This drawback has limited the applicable areas of the superheated steam generator.
Further, while the foregoing superheated steam generator is capable of generating high temperature steam, the efficiency of superheating the steam is poor. It was therefore difficult to produce a sufficient amount of steam for various uses, including heating and disinfecting of food products.